HACKERS: Update based on new version compare macros

Note the existence of these for people writing code.

HACKERS

@@ -204,20 +204,24 @@ Perl public API.
 
 =item Version numbers
 
-Version checking can be tricky to get correct (besides being buggy in some perl
-versions).
-C<ivers()> is used in the C<=tests> section to overcome this, and constructs
+Version checking used to be tricky to get correct (besides being buggy in some
+perl versions).
+C<ivers()> is used in the C<=tests> section to overcome this. and constructs
 like the following in the C language sections.
 
-  #if { VERSION < 5.9.3 }
+  #if PERL_VERSION_EQ(5,9,3)
+  #if PERL_VERSION_NE(5,9,3)
+  #if PERL_VERSION_LT(5,9,3)
+  #if PERL_VERSION_GT(5,9,3)
+  #if PERL_VERSION_LE(5,9,3)
+  #if PERL_VERSION_GE(5,9,3)
 
-instead of
+An alternative way of saying things like these is
 
-  #if ((PERL_VERSION < 9) \
-    || (PERL_VERSION == 9 && PERL_SUBVERSION < 3))
+  #if { VERSION < 5.9.3 }
 
-The version number can be either of the new form C<5.x.x> or the older
-form C<5.00x_yy>. Both are translated into the correct preprocessor
+In this form, the version number can be either of the new form C<5.x.x> or the
+older form C<5.00x_yy>. Both are translated into the correct preprocessor
 statements. It is also possible to combine this with other statements:
 
   #if { VERSION >= 5.004 } && !defined(sv_vcatpvf)